Methods for handling sheet material

ABSTRACT

In the feeding of sheet material to a machine such as a tire building former a sheet is first placed on a table and one edge of the sheet is aligned with a first datum line, preferably by tilting the table and supplying floatation air under the sheet. The sheet is then picked up and moved transversely through a predetermined distance by a gripping device to align the edge with a second datum line so as to enable the sheet to be fed in appropriate alignment to a machine.

This invention relates to methods and apparatus for handling sheetmaerial, particularly but not exclusively for use in the manufacture ofpneumatic tires.

In the manufacture of pneumatic tires it is necessary to wrap sheets ofmaterial such as plies of rubberized parallel-cord fabric around a tirebuilding former, and in order to obtain a uniform tire structure it isessential to feed the plies along an accurately predetermined path inpresenting them to the former. It is also important that the lenth ofeach ply and the circumference of the former are accurately matched soas to achieve a good joining relationship of the ends of the ply afterit has been wrapped aroudn the former. These requirements areparticularly difficult to satisfy in the practice of automatic methodsof tire building.

One object of the present invention is to provide a method of feeding asheet of ply material to a tire building former in which the alignmentof the ply is accurately determined, and a second object is to matchaccurately the length of the ply and the circumferential dimension ofthe former and any material already on the former.

According to one aspect of the invention, a method of feeding a sheet ofmaterial to a machine comprises laying the sheet on a table, arrangingthe sheet on the table to align an edge of the sheet with a first datumline, applying a gripping device to the sheet and moving the grippingdevice and the sheet in an alignment-preserving manner automatically toalign the said edge with a second datum line bearing a predeterminedrelationship to the first datum line and suitably positioned in relationto the said machine to enable the sheet to be fed in appropriatealignment to the machine.

In a preferred method in accordance with the invention the sheet ofmaterial is a ply of tire building fabric and the machine is a tirebuilding former. The alignment of a side edge of the ply with a firstdatum line on the table is preferably carried out, according to afurther feature of the invention, by transversely tilting the tablewhile providing a flow of air beneath the ply to permit it to float overthe table surface into appropriate alignment, against a raised sideabutment. Additionally, an end abutment may be provided, the associatedply end being moved into contact with the end abutment by longitudinallytilting the table while providing a flow of floatation air beneath theply.

Following the accurate placing of a ply on a table, the ply may be movedtransversely, for example by a vacuum gripping device, and positioned ona conveyor so that its position and alignment on the conveyor bears afixed relationship to the position and alignment which has beenestablished on the table. This position and alignment is arranged so thatthe conveyor may then be operated to feed the ply in accurate positionand alignment to a tire building former suitably located adjacent theconveyor.

In order to match the length of the ply and the circumference of theformer so as to achieve a good joining relationship of the ends of theply after it has been wrapped around the former, means may be providedto measure accurately the length of each ply and to adjust the diameterof the former if required.

The invention also provides apparatus for carrying out the method inaccordance with the invention, comprising a table, means for tilting thetable and for supplying floatation air to its surface so as to enable asheet of material on the table to be aligned with the edge of the sheetin alignment with a first datum line, and a gripping device for thesheet arranged to be movable in an alignment-preserving mannerautomatically to align the said edge with a second datum line bearing apredetermined relationship to the first datum line so as to enable thesheet to be fed in appropriate alignment to a machine.

In a preferred apparatus in accordance with the invention the machine isa tire building former.

One embodiment of the invention will now be described, by way ofexample, with reference to the accompanying drawings in which:

FIGS. 1 to 5 are diagrammatic plan views showing a ply alignment tablecarrying a ply in successive stages of alignment;

FIGS. 6 to 10 are diagrammatic end views of the ply alignment tablecorresponding respectively to FIGS. 1 to 5;

FIG. 11 is a diagrammatic end view showing the ply alignment table ofFIGS. 1 to 10 in association with a tire building former and conveyor,and

FIG. 12 is a side view of the apparatus shown in FIG. 11.

In the manufacture of a radial-ply pneumatic tire the carcass of thetire includes a ply of parallel-cord rubberized fabric in which thecords are arranged to run parallel to the axis of a tire buildingformer. In the operation of building a tire in accordance with themethod described in United Kingdom Application Publication No. 2,129,380dated May 16, 1984 a pair of tire bead elements are located coaxially atopposite ends of a bead tube in axially spaced relationship and anexpansible former around which tire carcass material is wrapped islocated coaxially within the tube in a predetermined position so thatthe tire carcass material projects axially beyond the bead elements ateach end of the former, the former then being expanded to cause thecarcass to contact the bead elements and to turn the projecting ends ofthe material radially outwardly around the bead elements.

In order to carry out this process it is necessary for a ply of carcassmaterial and an inner lining of rubber to be wrapped around theexpandible former in a predetermined axial position on the former andwith the cords of the ply in axial alignment. It is also necessary,particularly when the operation is carried out by automatic means, thatwhen the ply is wrapped around the former its ends meet in arelationship which is nearly exactly abutting.

In order to achieve the accurately predetermined location of the ply inthe axial sense relative to the former, a method as illustrated in theaccompanying drawings is operated as follows:

FIG. 1 and FIG. 6 show a floatation table 10 in a state where a ply 11has been placed in position on the table by a vacuum-operated grippingdevice 12 which is movable along an overhead track 13 (see FIG. 11) totransfer the ply from a temporary storage tray (not shown) to thefloatation table. The cords of the ply are roughly aligned parallel withthe shorter sides of the table 10.

The floatation table 10 is mounted on a sub-frame 15 by means of a balljoint 16 at one corner and by open location socket hinge joints 17, 18,19 at the remaining three corners. The joints 17 to 19 each comprise asemi-cylindrical member 20 (see FIG. 6) secured tot he table, whichengages a corresponding socket 21 secured to the sub-frame 15 to permittilting of the table about the axis of the member 20 while permittingthe component parts of the joint to separate when required, e.g. asshown in FIG. 7 where the joint 17 is illustrated in the separatedposition.

The arrangment of the table 10 is such that it may be tilted about alongitudinal axis through the joints 16 and 17 so as to move the ply 11transversely to the right as shown in FIGS. 1 and 2, and it may also betilted about a transverse axis through the joints 16 and 19 to move theply longitudinally as shown in FIG. 3. The table 10 is provided with aporous upper surface communicating with suitable ducts below the surfacethrough which compressed air may be supplied to provide floatation ofthe ply, enabling it to move easily over the table surface in whicheverdirection the table is tilted.

A datum line defined by spring-loaded pegs 23, 24, 25 is provided on thetable to constitute a first datum line for the ply, and similar pegs26,27 provide an abutment for positioning the forward edge of the ply.Alignment of one edge of the ply with the first datum line is achievedas shown in FIGS. 2 and 7 by tilting the table and supplying airfloatation to the underside of the ply. The tilting of the table isachieved by a pneumatic ram engaging the underside of the table at alift point 28 which is offset from the centre of the table so as toproduce initially a tilt about an axis through the joints 16,17, and anintermediate stop in the form of a stirrup 30 attached to the table atits upper end is positioned so that when the lower end 31 of the stirrupengages a suitable abutment (not shown) beneath the table, as seen inFIG. 7, the axis of tilt of the table is transferred to a line throughjoints 16,19. The relationship between the point 28 at which the liftingram applies its thrust and the position of the intermediate stop 30 issuch as to cause the table to tilt first about a diagonal axis throughthe joints 16,18, until the joint 19 is reengaged and then to continuetilting about the transverse axis through the joints 16 and 19 as shownin FIG. 8.

After the tilting action illustrated in FIG. 8 has been completed, theforward end edge 35 of the ply 11 will have moved into engagement withthe pegs 26,27, thus locating the ply in a predetermined position bothwith respect to its side edge 36 and its forward end edge 35. In thisposition, the air floatation of the ply is terminated so that the plysettles into a resting position on the table, as illustrated in FIGS. 9and 10. The table is then lowered slowly until it is horizontallydisposed, thus preserving the accurate location of the ply.

As shown in dotted lines in FIG. 11 the gripping device 12 is located ina predetermined position above the table 10 and carries photo-electriccells 40-43. The photo-elective cells 40-43 are connected in anelectrical control system, providing data which confirms that theposition of the ply as shown in FIGS. 4 and 5 is in fact in the correctpredetermined location and alignment. The gripping device may then beoperated so as to pick up the ply by means of a vacuum suction device(not illustrated) and hole the ply in a flat condition against theunderside of a flat shoe 50 of similar area to the table 10.

The gripping device 12 is then moved to the full-line position shown inFIG. 11 above a conveyor 55, holding the edge 36 of the ply in alignmentwith a second datum line (not shown), parallel to the first datum line,which is arranged to have an accurately predetermined relationship witha tire building former 56. Adjustable stops 60,61 are provided to enablethe relationship of the positions of the gripping device 12 adjacent thetable 10 and the building former 56 respectively to be accuratelypredetermined, thus determining the position of the second datum line inrelationship to the building former. The gripping device 12 is thenoperated to deposit the ply 11 on the conveyor 55 without disturbing itslocation and alignment.

After the gripping device 12 has been disengaged from the ply 11,leaving it on the conveyor 55, the position of the ply is again checkedby the photo-electric cells 40-43. The conveyor 55 comprises an endlessbelt 65 passing around fixed rollers 66,67,68,69,70 and a movable roller71 which can tighten the belt in lapping relationship with the former 56as shown in FIG. 12 and which can be lowered to release the belt fromthe former to enable the former to be withdrawn from the conveyor aftera ply 11 has been transferred to it. Means is provided for driving thebelt so that its upper run moves towards the former carrying the plyaround the former so that it adheres to the surface of a rubber innerlining which has already been applied to the former 56 at a previousstage of the tire building process.

The photo-electric cells 43 and 40 are spaced apart at an accuratelypredetermined distance and are arranged to provide signals to a controlsystem as the leading end 35 and the trailing end 75 of each ply 11passes the photo-electric cells 43 and 40 respectively, the controlsystem including a rotary encoder driven from the belt surface so that ameasurement of the length of the ply 11 may be determined before the plyhas been wrapped around the former 56. Means (not illustrated) isprovided for controlling and adjusting the diameter of the former 56,which may be of the type incorporating radially movable segments underthe control of a motor-driven expander mechanism so as to match thecircumference of the former and any material carried thereon (i.e. arubber liner) to the length of the particular ply which is being fed toit. By this means, it is possible to achieve a good joint between theends of the ply when it has been fully transferred to the former.

The method and appartatus described above has the advantage that itenables sheets of parallel-cord ply material to be fed in an accuratelypredetermined location with one edge in accurate alignment with apredetermined circumferential line around the building former 56 asdetermined by the position of the adjustable stop 61.

Should the ply be of dimensions or shape which are outside the permittedtolerances, this can be detected by the photo-electric cells 40-43 andthe ply can be rejected, for example by reversing the conveyor 53.

While in the specific example described above the invention is appliedto the handling of ply fabric for pneumatic tire carcasses, it may alsobe used for handling other tire building components, or components forincorporation into other products of the rubber industry such assuspension bellows, or any other industrial applicaiton where sheetmaterial is required to be fed in accurate relationship to a machine.The component may have a not-rectangular shape, such as a bias-cut plyand in this case one side edge is aligned as described above, and theleading edge may be positioned against a single abutment.

We claim:
 1. A method of feeding a ply of tire building fabric to a tirebuilding former comprising laying a ply of fabric onto a table at afirst location, transversely tilting the table while providing a flow ofair beneath the ply to permit the ply to float over the table surfaceinto appropriate alignment against a raised side abutment of the tablethus arranging the ply on the table to align one side edge of said plywith a first datum line, applying a gripping device to the ply andtransversely moving the gripping device and ply in an alignmentpreserving manner to a second location to align said one edge with asecond datum line parallel with the first datum line and which is inpredetermined relationship to a tire building former to enable the plyto be fed in appropriate axial alignment to the former.
 2. A methodaccording to claim 1 wherein an end of the ply is moved into contactwith an end abutment by longitudinally tilting the table while providinga flow of floatation air beneath the ply.
 3. A method according to claim1 wherein the ply is moved transversely by a gripping device andpositioned thereby on a conveyor so that its position and alignment onthe conveyor bears a fixed relationship to the position and alignmentwhich has been established on the table, the conveyor then beingoperated to feed the ply in an accurate position and alignment to a tirebuilding former located adjacent the conveyor.
 4. A method according toclaim 3 wherein the length of the ply is measured and the diameter ofthe former is controlled to match the circumference of the former andany material carried thereon to the length of the ply.